Pump system including a variable frequency drive controller

ABSTRACT

A pump system generally comprising an electrical connector operable to couple with an electric circuit to receive electricity, an electric motor operable to actuate a pump to pump a fluid, and a variable frequency drive (VFD) controller. The VFD controller is operable to control the rotational speed of the electric motor by providing a variable frequency signal to the electric motor to prevent the current utilized by the electric motor from exceeding a maximum current level associated with the electric circuit.

BACKGROUND

1. Field

Embodiments of the present invention relate to pump systems. More particularly, various embodiments of the invention provide a pump system including a variable frequency drive controller.

2. Description of the Related Art

Pump systems are often used to transfer and/or filter fluids and lubricants. For example, lubricant pump systems may be used to transfer a lubricant from a supplier's delivery container into a customer's storage tank. Due to temperature changes and the wide range of viscosities presented by commonly-used lubricants, electric lubricant pump systems often must operate at low and fixed flow rates to keep motor loads under available circuit limits. Utilization of low flow rates forces these systems to operate for extended and undesirable periods of time. Air operated lubricant pumps have been developed to more rapidly pump lubricants having variable viscosities. However, it is often desirable to utilize electric lubricant pumping systems instead of air operated pumping systems.

SUMMARY

In various embodiments, the present invention provides a pump system generally comprising an electrical connector operable to couple with an electric circuit to receive electricity, an electric motor operable to actuate a pump to pump a fluid, and a variable frequency drive (VFD) controller. The VFD controller is operable to control the rotational speed of the electric motor by providing a variable frequency signal to the electric motor to prevent the current utilized by the electric motor from exceeding a maximum current level associated with the electric circuit.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Various embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a front perspective view of a portable lubricant pump system configured in accordance with various embodiments of the present invention;

FIG. 2 is an environmental view of some of the components of the pump system of FIG. 1;

FIG. 3 is a block diagram of some of the components of the pump system of FIG. 1;

FIG. 4 is a schematic diagram of some of the components of the pump system of FIG. 1; and

FIG. 5 is a front perspective view of a portable lubricant pump system configured in accordance with various other embodiments of the present invention.

The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating various embodiments of the invention.

DETAILED DESCRIPTION

The following detailed description of various embodiments of the invention references the accompanying drawings which illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

Referring initially to FIG. 1, various embodiments of the present invention provide a pump system 10 configured for pumping a fluid. For example, the pump system 10 may be operable to transfer the fluid from one container, such as a drum D, to another container, such as a holding tank T. While embodiments of the present invention are particularly well suited for pumping and/or transferring lubricants and related viscous fluids, such as engine oils, gear oils, antifreeze, and the like between containers typically utilized in a lubricant retailer's business, such as conventional fifty-five gallon drums and metered tanks or bins found in an automobile service or lubrication shop, these principles are not so limited and equally apply to the transfer, pumping, and/or filtering of any fluid in any setting.

The pump system 10 may be configured to pump low, medium, and high viscosity fluids utilizing a pump 12. For example, the pump system 10 may be configured to pump fluids having various viscosities, including low viscosities (e.g., less than about 230 cps; 5W to 10W engine oils), medium viscosities (e.g., between about 230 cps and about 600 cps; 10W-30 or 10W-40 engine oils), and/or high viscosities (e.g., up to about 4900 cps; 80W, 90W, 120W, or 680W gear oils). However, the pump system 10 may be operable to pump viscous and non-viscous fluids of any viscosity and is not limited to the exemplary viscosities provided above.

The pump 12 may be coupled with an electric motor 14 through a drive assembly 16 to enable pumping of the viscous fluid. The pump 12 may be a positive displacement pump that can operate at varying speeds to pump fluids at rates ranging up to one-hundred gallon per minute or more. In some embodiments, the pump 12 is an internal gear pump driven by rotating drive shaft associated with the drive assembly 16. The pump 12 includes an inlet 18 and an outlet 20. If a positive displacement pump is utilized, it need not be an internal gear pump, but could be an external gear pump or a vane pump. However, any other suitable type of pump may be utilized by embodiments of the present invention. The pump 12 may include a by-pass valve that releases fluid from the pump 12 when a certain pressure is reached to prevent pressure buildup. The pump 12 may be associated with various hose assemblies to facilitate pumping liquids between containers.

When the drive assembly 16 is actuated by the electric motor 14 to rotate the drive shaft or other drive elements, fluid is pressurized between the inlet 18 and the outlet 20 causing fluid to flow into the inlet 18, and out of the outlet 20. The drive assembly 16, drive shaft, and/or other drive elements may present any configuration operable to actuate the pump 12 using the electric motor 14. For example, the drive assembly 16 may include the variable speed transmission assemblies disclosed in U.S. patent application Ser. No. 11/163,698, filed Oct. 27, 2005, which is incorporated herein by specific reference. However, in some embodiments, the drive assembly 16 may be substantially conventional in configuration or utilize a constant-speed transmission and/or other direct-drive transmissions.

The electric motor 14 is operable to be controlled by a variable frequency drive (VFD) controller 22 to actuate the pump 12. The rotational speed of the electric motor 14 is governed by the frequency of a power signal provided by the VFD controller 22. As is discussed in more detail below, the VFD controller 22 is operable to control the rotational speed of the electric motor 14 using the frequency of the power signal to prevent the current utilized by the electric motor 14 from exceeding a maximum current level of an electric circuit that powers the pump system 10.

The electric motor 14 may include any element or combination of elements operable to rotate based on the power signal provided by the VFD controller 22. In some embodiments, the electric motor 14 may include an alternating current (AC) motor having a single-phase or three-phase induction configuration. However, in some embodiments, the electric motor 14 may include an AC synchronous motor. The electric motor 14 may also include an ammeter operable to monitor the current draw of the electric motor 14, as is discussed in more detail below. The electric motor 14 may also include or be coupled with a DC motor, such as a brushless DC motor.

In some embodiments, the electric motor 14 may present a power output of between about 0.25-10 hp, between about 0.5-5 hp, or about 2 hp. The electric motor 14 may be operable to rotate the drive shaft within the range of 1000-3000 RPM and/or between about 1500-2500 RPM. However, the particular power and speed provided by the electric motor 14 will depend on its particular configuration and embodiments of the present invention may employ electric motors presenting any power and speed. The motor 14 may be an enclosed fan-cooled motor to prevent any debris or foreign objects from fouling its operation.

The VFD controller 22 and/or electric motor 14 may be coupled with a connector 24 to acquire an electrical input signal to power various elements of the pump system 10. The connector 24 may connect with the electric circuit using connecting elements such as plugs, sockets, cables, wires, combinations thereof, and the like. In some embodiments, the connector 24 may be a cable including a plug for reception by a conventional 15 or 20 amp (at 115V or 220V) electric circuit socket to acquire the input signal for use by the pump system 10. Such a configuration enables the pump system 10 to be easily powered by readily-available power sources. However, the connector 24 may be adapted to couple with batteries and/or other circuit configurations instead of, or in addition to, coupling with 15 or 20 amp electric circuits.

In some embodiments, the connector 24 may be associated with a voltage sensor 26 that is operable to monitor the voltage provided by the electric circuit—such as the voltage of the input signal. For example, as is discussed in more detail below, the voltage sensor 26 may be adapted to detect when the voltage provided by the electric circuit drops to enable the VFD controller 22 to take proper corrective action. The voltage sensor 26 may be any element or combination of elements operable to sense the voltage provided by the electric circuit to the connector 24. For example, the voltage sensor 26 may include a voltmeter that is coupled with the connector 24 and/or VFD controller 22 to measure supplied voltage. The voltage sensor 26 may include digital and/or analog components to measure voltage, including potentiometers, null detectors, integrated circuits and other digital components such as operational amplifiers, discrete analog and digital logic, combinations thereof, and the like. In some embodiments, the voltage sensor 26 may be integral with the VFD controller 22 or otherwise comprise a portion of the VFD controller 22. The voltage sensor 26 may continuously or periodically measure the voltage provided by the electric circuit and provide a corresponding analog and/or digital signal for use by the VFD controller 22.

The VFD controller 22 is coupled with the connector 24 and electric motor 14 and is operable to provide the power signal to the electric motor 14 to control its operation and rotational speed. As illustrated in FIG. 4, the VFD controller 22 may utilize the electrical input signal provided by the connector 24 from the electric circuit to generate the power signal with a particular frequency to cause the electric motor 14 to rotate at a desired speed (RPM). For example, the rotational speed of the electric motor 14 may be determined by the frequency of the power signal and the number of poles in the stator winding:

${{RPM} = \frac{120 \times f}{p}},$

where RPM is the rotational speed of the electric motor 14 in revolutions per minute, f is the frequency of the power signal in hertz, and p is the number of poles in the stator winding of the electric motor 14. As p is constant, the VFD controller 22 may vary the rotational speed of the electric motor 14 by varying the frequency of the power signal. For example, an increase in the frequency of the power signal will result in an increase in the rotational speed of the electric motor 14.

The VFD controller 22 may include any elements or combination of elements operable to receive the input signal from the connector 24 and generate the power signal with a desired frequency. In some embodiments, the VFD controller 22 may include various solid state devices, such as semiconductor switches, rectifiers, inverters, phase converters, diode bridges, combinations thereof, and the like, to convert the AC input signal into the desired power signal. For example, the VFD controller 22 may convert the AC input signal provided by the connector 24 into an intermediate DC signal for conversion into a quasi-sinusoidal AC power signal for use by the electric motor 14. The VFD controller 22 may additionally or alternatively provide a DC signal to power the electric motor 14.

In some embodiments, the VFD controller 22 may additionally or alternatively include a microcontroller, microprocessor, programmable logic device, digital signal processor, analog and digital logic, combinations thereof, and the like, to generate the desired power signal for use by the electric motor 14. The VFD controller 22 may be implemented in hardware, software, and/or combinations thereof. For example, the VFD controller 22 may comprise software operable to be executed by one or more processing and/or control devices to function conventional pumping elements in a desired manner.

In some embodiments, the pump system 10 may include a plurality of inputs to facilitate operation of the VFD controller 22. For example, to acquire the maximum current level associated with the electric circuit, the pump system 10 may include a maximum current input 28 operable to be functioned by the operator to set the maximum current level associated with the electric circuit. The maximum current input 28 may comprise one or more functionable inputs, such as buttons, dials, and switches, which may be functioned by the operator to set the maximum current level. In some embodiments, as illustrated in FIG. 2, the maximum current input 28 may comprise a toggle switch operable to toggle between 15 amp and 20 amp circuit settings. Additionally or alternatively, the maximum current input 28 may present other interfaces for receiving the maximum current level from the operator or external devices. For example, the maximum current input 28 may include a keyboard, a touch screen display associated with the VFD controller 22, voice recognition elements, combinations thereof, and the like.

The inputs associated with the pump system 10 may additionally or alternatively include a rotational speed input 30 and a mode input 32. The rotational speed input 30 is operable to be functioned to set a desired speed of the electric motor 14 or other performance characteristic of the pump system 10, such as a desired output pressure. The rotational speed input 30 may comprise one or more functionable inputs, such as buttons, dials, and switches. For example, the rotational speed input 30 may include a dial operable to be functioned by the operator to set a desired rotational speed, such as between 0 to the maximum rotational speed operable to be achieved by the electric motor 14 and pump 12. The VFD controller 22 may utilize signals provided by the rotational speed input 30 to match the speed of the electric motor 14 to the set speed, as is discussed in more detail below. In some embodiments, the rotational speed input 30 may correspond to a sensed characteristic of the viscous fluid pumped by the pump 12 to allow the operator to instruct the VFD controller 22 to match the indicated characteristic. For example, the rotational speed input 30 may be functioned to set a desired output pressure and/or output pressure percent corresponding to the output pressure of the pumped viscous fluid.

To allow the VFD controller 22 to match the characteristic set by the rotational speed input to one or more sensed characteristics, the pump system 10 may include an output sensor 34 operable to sense a characteristic of the pumped viscous fluid. For example, the output sensor 34 may be operable to sense a pressure of the pumped viscous fluid to allow the VFD controller 22 to control the rotational speed of the electric motor 14 to produce a pumped viscous fluid pressure that corresponds to the viscous fluid pressure indicated by the operator utilizing the rotational speed input 30. Additionally or alternatively, the output sensor 34 and rotational speed input 30 may correspond to other characteristics relating to the pumped viscous fluid, such as flow rate, flow volume, fluid temperature, fluid density, combinations thereof, and the like. Thus, the operator may easily control the output pressure, or other characteristics of the pumped viscous fluid, by functioning the rotational speed input 30 to facilitate in filtering and other pumping applications to, for example, extend and/or optimize the life and functionality of the pump system 10.

The output sensor 34 may include any element or elements operable to sense one or more characteristics of the pumped viscous fluid. For example, in some embodiments the output sensor 34 may include a pressure transducer operable to sense a pressure of the pumped viscous fluid. However, in other embodiments, the output sensor 34 may additionally or alternatively include a thermometer, a digital or analog scale, a flow sensor, a volume sensor, a density sensor, combinations thereof, and the like.

The mode input 32 is operable to be functioned by the operator to select a desired operating mode for the pump system 10. For example, the mode input 32 may be functioned to select an automatic mode or a manual mode. If the automatic mode is selected, the VFD controller 22 is operable to control the rotational speed of the electric motor 14 based upon one or more characteristics sensed by the output sensor 34.

For instance, if automatic mode is selected, the VFD controller 22 can control the electric motor 14 to present a generally constant output pressure by forming a feedback loop with the output sensor 34 while preventing the current utilized by the electric motor 14 from exceeding the set maximum current level. Further, in automatic mode, the VFD controller 22 can control the electric motor 14 to correspond to the desired characteristic set by the rotational speed input 30. For example, the operator may set a desired output pressure percent utilizing the rotational speed input 30 and the VFD controller 22 may control the rotational speed of the electric motor 14 to generally match the desired output pressure percent based upon feedback provided by the output sensor 34. The VFD controller 22 is not limited to controlling the electric motor 14 based on output pressure as the VFD controller 22 may form a feedback loop with the output sensor 34 to automatically control the electric motor 14 to produce any generally constant output characteristic including flow rate, flow volume, fluid temperature, fluid density, combinations thereof, and the like.

If manual mode is selected, the VFD controller 22 is operable to control the rotational speed of the electric motor 14 to match the rotational speed set by the rotational speed input 30 while preventing the current utilized by the electric motor 14 from exceeding the set maximum current level. Thus, for example, if the rotational speed input 30 indicates a particular RPM, the VFD controller 22 may control the rotational speed of the electric motor 14 to match the indicated RPM. Similarly, if the rotational speed input 30 indicates a speed or pressure percentage, the VFD controller 22 may control the rotational speed of the electric motor 14 based on the indicated percentage, such as by controlling the electric motor 14 to produce half its maximum RPM when 50% is selected using the rotational speed input 30. As such, the pump system 10 may be placed in automatic mode to control the speed of the electric motor 14 based on a characteristic sensed by the output sensor 34 and a desired characteristic indicated by the rotational speed input 30 or be placed in manual mode to control the speed of the electric motor 14 based on a desired speed indicated by the rotational speed input 30.

In automatic mode, manual mode, or in embodiments where the pump system 10 does not present different operating modes, the VFD controller 22 is operable to control the rotational speed of the electric motor 14 by providing the variable frequency power signal to the electric motor 14 to prevent the current utilized by the electric motor 14 from exceeding the maximum current level associated with the electric circuit. Such functionality enables the pump system 10 to be easily utilized by the operator without overloading the electric circuit or tripping breakers associated with the electric circuit.

In some embodiments, the VFD controller 22 may acquire the maximum current level associated with the electric circuit from the maximum current input 28. For example, the operator may function the maximum current input 28 to indicate that the maximum current associated with the electric circuit is 15 A. Based on this input, the VFD controller 22 may control the rotational speed of the electric motor 14 using the frequency of the power signal to ensure that the electric motor 14 does not draw more than the indicated maximum current.

In some embodiments, the VFD controller 22 may include a memory having a look-up table that correlates current draw with rotational speed for the particular electric motor 14 utilized by the pump system 10. Such a configuration enables the VFD controller 22 to rapidly determine the proper rotational speed to prevent the current utilized by the electric motor 14 from exceeding the maximum current level associated with the electric circuit. Additionally or alternatively, the VFD controller 22 may receive information from the ammeter associated with the electric motor 14 to monitor the current utilized by the electric motor 14 in real time to increase or decrease the frequency of the power signal accordingly. In some embodiments, the VFD controller 22 may be operable to directly calculate the current utilized by the electric motor 14 based on the rotational speed of the electric motor 14 without using the look-up table, such as by utilizing formulas and equations that associate current use with rotational speed.

To identify an available current level associated with the electric circuit, the VFD controller 22 may use information provided by the voltage sensor 26. For example, the VFD controller 22 and/or voltage sensor 26 may detect a drop in the voltage provided by the electric circuit which in turn indicates a drop in the available current level associated with the electric circuit as changes in voltage and current are proportional where resistance/inductance is generally constant. For example, a circuit rated at 15 A may be able to only provide less than 15 A of current depending on supply and load conditions. Thus, the VFD controller 22 can control the rotational speed of the electric motor 14 to prevent the current utilized by the electric motor 14 from exceeding the available current level as calculated by the VFD controller 22 using the voltage sensor 26. However, the VFD controller 22 may determine the maximum and available current levels associated with the electric circuit based on the maximum current input 28, by utilizing the voltage sensor 26, by accessing data within its memory, by utilizing a default value, combinations thereof, and the like.

Thus, even where the viscosity of the pumped viscous fluid varies greatly, the pump system 10 may be utilized to pump the fluid without overloading the electric circuit or requiring tedious manual supervision and control by the operator as in both manual and automatic modes the VFD controller 22 will prevent the current utilized by the electric motor 14 from exceeding the maximum available current of the electric circuit.

The VFD controller 22 may also be operable to monitor overload conditions associated with the electric motor 14 to prevent the electric motor 14 from operating at high loads or excessively slow speeds for extended periods of time which may cause the electric motor 14 to overheat. If an overload condition is detected by the VFD controller 22, it may automatically shut the electric motor 14 down to prevent overheating and associated motor damage. The VFD controller 22 may monitor load conditions by monitoring current draw, rotational speed, motor temperature, flow rate, flow density, combinations thereof, and the like.

As illustrated in FIGS. 1 and 5, the pump system 10 may include a wheeled cart 36 to render the pump system 10 portable for easy transport. The wheeled cart 36 may include a wheel assembly 38 including an axle and a pair of rotatable wheels mounted on the opposing ends of the axle. The wheels may include hubs mounted on the axle for rotation and pneumatic tires mounted on the hubs to provide adequate support and easy maneuverability of the pump system 10. Thus, wheeled cart 36 may present the form of a hand cart or dolly to which various elements of the pump system 10 may be mounted or otherwise secured. However, in other embodiments, the pump system 10 may be non-portable and fixed in place.

In some embodiments, the pump system 10 may include a filtering element 40 operable to at least partially filter the viscous fluid pumped by the pump 12. The filtering element 40 may be coupled with the outlet 20 of the pump 12 to receive and filter pumped viscous fluids. The filtering element 40 may include any filter or combination of filters operable to at least partially filter the pumped viscous fluid. For example, the filtering element 40 may include a kidney loop filtration system having one or more filters with a beta ratio greater than 200 to achieve a desired ISO cleanliness level. The filtering element 40 may additionally or alternatively include one, two, four, and six element depth filters and/or 3-20 micron cartridge filter elements.

The VFD controller 22 may control the rotational speed of the electric motor 14, and thus the flow rate of the pumped viscous fluid, to ensure proper filtering. For example, the VFD controller 22 may operate the electric motor 14 at the maximum available speed without exceeding the maximum current provided by the electric circuit to reduce filtering times and stir up sediment that may be disposed on the bottom of fluid-holding containers such as the drum D and tank T. As the filtering element 40 may provide better filtration at low flow rates, the operator may function the inputs 28, 30, and/or 32 to achieve any desired amount of filtration. Thus, the pump system 10 is not required to operate the electric motor 14 at a single speed due to electric current limitations.

In operation, the operator may transport the pump system 10 to a container having the viscous fluid such as the tank T and/or drum D. The operator may couple the pump inlet 18 with the container and couple the pump outlet 20 with the same container to filter the viscous fluid held by the container or with another container, such as the drum D, to transfer the viscous fluid. In some embodiments, the operator may determine the maximum current level associated with the electric circuit to which the pump system 10 will be connected and function the maximum current input 28 accordingly. The operator may couple the connector 24 with the electric circuit to provide power to the pump system 10. In some embodiments, the operator may select an operating mode for the system 10, such as the automatic or manual modes discussed above. After coupling the connector 24 with the electric circuit, the operator may function the VFD controller 22 to start pumping the viscous fluid. The VFD controller 22 provides the power signal to the electric motor 14 to cause actuation of the pump 12 and pumping of the viscous fluid. The VFD controller 22 is operable to vary the frequency of the power signal to control the rotational speed of the electric motor 14 to prevent the current utilized by the electric motor 14 from exceeding the maximum current level associated with the electric circuit. In embodiments including the voltage sensor 26, the VFD controller 22 may monitor the voltage of the electric circuit to determine the maximum current level associated with the electric circuit in the event that the electric circuit is unable to provide current at the level indicated by the maximum current input 28.

In embodiments where the automatic mode is selected, the VFD controller 22 may control the electric motor 14 based on one or more characteristics sensed by the output sensor 34 while also preventing the current utilized by the electric motor 14 from exceeding the maximum current level associated with the electric circuit. In embodiments where the manual mode is selected, the VFD controller 22 may control the electric motor 14 based on rotational speed input 30 while also preventing the current utilized by the electric motor 14 from exceeding the maximum current level associated with the electric circuit. The viscous fluid may be pumped through the filtering element 40 for filtering purposes.

Thus, the pump system 10 is operable to pump low, medium, and high viscosity fluids under varying temperature conditions without tripping the circuit breakers associated with the electric circuit due to the motor control provided by the VFD controller 22. The pump system 10 may also pump any fluids of any viscosity at a desired flow rate to ensure proper filtration by the filtering element 40 to extend the life and optimize the filtration provided by the filtering element 40 while properly maintaining the current utilized by the electric motor 14.

It is believed that embodiments of the present invention and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes. 

1. A pump system comprising: an electrical connector operable to couple with an electric circuit to receive electricity; an electric motor operable to actuate a pump to pump a fluid; and a variable frequency drive (VFD) controller coupled with electric motor and connector, the VFD controller operable to control the rotational speed of the electric motor by providing a variable frequency signal to the electric motor to prevent the current utilized by the electric motor from exceeding a maximum current level associated with the electric circuit.
 2. The system of claim 1, further including a maximum current input coupled with the VFD controller, the maximum current input operable to be functioned to set the maximum current level.
 3. The system of claim 1, further including a voltage sensor operable to monitor the voltage provided by the electric circuit, the VFD controller being coupled with the voltage sensor and operable to calculate an available current level associated with the electric circuit and control the rotational speed of the electric motor to prevent the current utilized by the electric motor from exceeding the calculated available current level.
 4. The system of claim 1, further including a rotational speed input operable to be functioned to set a rotational speed, the VFD controller being coupled with the rotational speed input and operable to control the rotational speed of the electric motor to match the set rotational speed while preventing the current utilized by the electric motor from exceeding the maximum current level.
 5. The system of claim 1, further including— a mode input operable to be functioned to select an automatic mode or a manual mode, and an output sensor operable to sense a characteristic of the pumped fluid, the VFD controller being coupled with the mode input and output sensor and, if the automatic mode is selected, control the rotational speed of the electric motor based upon the sensed characteristic while preventing the current utilized by the electric motor from exceeding the maximum current level.
 6. The system of claim 5, wherein the sensed characteristic is a pressure of the pumped fluid and the VFD controller is operable to control the rotational speed of the electric motor to produce a generally constant pumped fluid pressure while preventing the current utilized by the electric motor from exceeding the maximum circuit current level.
 7. The system of claim 1, further including a filtering element operable to at least partially filter the pumped fluid.
 8. The system of claim 1, further including a wheeled cart, the electrical connector, electric motor, and VFD controller being mounted on the cart.
 9. A pump system comprising: an electrical connector operable to couple with an electric circuit to receive electricity therefrom; a maximum current input operable to be functioned to set a maximum circuit current level; a mode input operable to be functioned to select an automatic mode or a manual mode; a pump; an electric motor operable to actuate the pump to pump a fluid; an output sensor operable to sense a characteristic of the pumped fluid; and a variable frequency drive (VFD) controller coupled with the inputs, output sensor, and electric motor, the VFD controller operable to control the rotational speed of the electric motor by providing a variable frequency signal to the electric motor to prevent the current utilized by the electric motor from exceeding the set maximum circuit current level and, if the automatic mode is selected, control the rotational speed of the electric motor based upon the sensed characteristic.
 10. The system of claim 9, wherein the sensed characteristic is a pressure of the pumped fluid and the VFD controller is operable to control the rotational speed of the electric motor to produce a generally constant pumped fluid pressure while preventing the current utilized by the electric motor from exceeding the set maximum circuit current level.
 11. The system of claim 9, further including a rotational speed input operable to be functioned to set a rotational speed, the VFD controller being coupled with the rotational speed input and, if the manual mode is selected, control the rotational speed of the electric motor to match the set rotational speed while preventing the current utilized by the electric motor from exceeding the set maximum current level.
 12. The system of claim 9, further including a voltage sensor operable to monitor the voltage provided by the electric circuit, the VFD controller being coupled with the voltage sensor and operable to calculate an available current level associated with the electric circuit and control the rotational speed of the electric motor to prevent the current utilized by the electric motor from exceeding the calculated available current level.
 13. The system of claim 8, further including a filtering element, the pump being operable to pump the fluid through the filtering element to at least partially filter the fluid.
 14. The system of claim 8, further including a wheeled cart, the electrical connector, inputs, electric motor, and controller being mounted on the cart.
 15. A method of pumping a fluid, the method comprising: pumping a fluid using a electric motor powered by an electric circuit; and controlling the rotational speed of the electric motor by providing a variable frequency signal to the electric motor to prevent the current utilized by the electric motor from exceeding a maximum current level associated with the electric circuit.
 16. The method of claim 15, further including acquiring the maximum current level associated with the electric circuit from a functionable input.
 17. The method of claim 15, further including monitoring the voltage provided by the electric circuit, calculating an available current level associated with the electric circuit, and controlling the rotational speed of the electric motor to prevent the current utilized by the electric motor from exceeding the calculated available current level.
 18. The method of claim 15, further including acquiring a rotational speed input and controlling the rotational speed of the electric motor to match the acquired rotational speed while preventing the current utilized by the electric motor from exceeding the maximum current level.
 19. The method of claim 15, further including sensing a characteristic of the fluid pumped by the electric motor and controlling the rotational speed of the electric motor based upon the sensed characteristic while preventing the current utilized by the electric motor from exceeding the maximum current level.
 20. The method of claim 19, wherein the sensed characteristic is a pressure of the pumped fluid and the rotational speed of the electric motor is controlled to produce a generally constant pumped fluid pressure.
 21. The method of claim 15, further including pumping the fluid through a filtering element to at least partially filter the fluid. 